A wireless charging technology is a technology of transmitting power required to wirelessly charge a battery without using a power supply code or a charging connector.
Recently, with an explosive increase in a smart phone market, a use of a wireless charging technology has been accelerated. The smart phone enables a user to freely enjoy abundant contents and multimedia any time, but has a short use time due to a restriction of battery capacity. The environment of the wireless charging technology in a smart phone market has been greatly changed with the appearance of a wireless charging correspondence smart phone from 2010, and products with a wireless charging module for the purpose of wirelessly charging a mobile phone and a smart phone have been continuously published at home and abroad in 2011. In addition, an electric toothbrush, an electric razor, or the like are charged based on an electromagnetic induction principle. Recently, wireless charging products that may charge mobile devices, such as a mobile phone, a PDA, an MP3 player, and a notebook computer, using the electromagnetic induction have been released.
Among the wireless charging modes, a magnetic induction mode that induces a current from one coil to another coil through a magnetic field is very sensitive to a distance and a relative position between the coils and therefore has suddenly reduced transmission efficiency even though the two coils have a slight distance from each other or deviate from each other. Therefore, there is a problem in that the charging system based on the magnetic induction mode may be used only in a close range of several centimeters (cm) or less.
Meanwhile, as another mode, there is a non-radial energy transfer mode based on coupling of attenuation waves of a resonance field. The non-radial energy transfer mode uses the fact that two resonators having the same frequency do not affect other non-resonators therearound but have a tendency to be coupled with each other. As a result, the non-radial energy transfer mode has been introduced as a technology of transferring energy to a farther distance than the typical electromagnetic induction mode.
As such, a wireless power transmitter needs to provide an appropriate charging mode conforming to a mode which is supported by a power receiving apparatus among different charging modes.